CLN: Remove __future__ imports

[jschendel]

• xref CLN: remove PY2 #25725
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff

Not needed after dropping Python 2.

[codecov]

Codecov Report

Merging #25889 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #25889      +/-   ##
==========================================
- Coverage   91.47%   91.47%   -0.01%     
==========================================
  Files         175      175              
  Lines       52885    52863      -22     
==========================================
- Hits        48379    48358      -21     
+ Misses       4506     4505       -1

Flag	Coverage Δ
#multiple	90.04% <ø> (-0.01%)	⬇️
#single	41.8% <ø> (-0.03%)	⬇️

Impacted Files	Coverage Δ
pandas/plotting/_style.py	77.41% <ø> (-0.25%)	⬇️
pandas/core/frame.py	96.79% <ø> (-0.01%)	⬇️
pandas/io/formats/terminal.py	31.7% <ø> (-0.83%)	⬇️
pandas/plotting/_misc.py	38.46% <ø> (-0.23%)	⬇️
pandas/io/formats/format.py	97.99% <ø> (-0.01%)	⬇️
pandas/core/algorithms.py	94.78% <ø> (-0.01%)	⬇️
pandas/io/formats/latex.py	100% <ø> (ø)	⬆️
pandas/core/window.py	96.4% <ø> (-0.01%)	⬇️
pandas/core/series.py	93.67% <ø> (-0.01%)	⬇️
pandas/core/arrays/sparse.py	92.17% <ø> (-0.01%)	⬇️
... and 13 more

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[codecov]

Codecov Report

Merging #25889 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #25889      +/-   ##
==========================================
- Coverage   91.47%   91.47%   -0.01%     
==========================================
  Files         175      175              
  Lines       52885    52863      -22     
==========================================
- Hits        48379    48358      -21     
+ Misses       4506     4505       -1

Flag	Coverage Δ
#multiple	90.04% <ø> (-0.01%)	⬇️
#single	41.8% <ø> (-0.03%)	⬇️

Impacted Files	Coverage Δ
pandas/plotting/_style.py	77.41% <ø> (-0.25%)	⬇️
pandas/core/frame.py	96.79% <ø> (-0.01%)	⬇️
pandas/io/formats/terminal.py	31.7% <ø> (-0.83%)	⬇️
pandas/plotting/_misc.py	38.46% <ø> (-0.23%)	⬇️
pandas/io/formats/format.py	97.99% <ø> (-0.01%)	⬇️
pandas/core/algorithms.py	94.78% <ø> (-0.01%)	⬇️
pandas/io/formats/latex.py	100% <ø> (ø)	⬆️
pandas/core/window.py	96.4% <ø> (-0.01%)	⬇️
pandas/core/series.py	93.67% <ø> (-0.01%)	⬇️
pandas/core/arrays/sparse.py	92.17% <ø> (-0.01%)	⬇️
... and 13 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 95c78d6...9510dd8. Read the comment docs.

[jreback]

thanks!